1. Technical Field
The present invention relates to apparatus for analyzing biologic fluid samples in general, and to containers for holding a biologic fluid sample during analytical procedures in particular.
2. Background Information
Most analytical methods for evaluating constituents within a biologic fluid sample require that the sample be substantially diluted prior to evaluation. A typical chemical analysis, for example, involves placing a substantially diluted sample into a transparent cuvette of known dimensions and constant light path for evaluation. The cuvette can be made from glass or a hard acrylic that is ground or otherwise manufactured to tight tolerances. The tight tolerances, which are necessary to insure the accuracy of the light path through the cuvette, also make the cuvette undesirably expensive. In hematological analyses, a substantially diluted sample is typically passed through a flow cell within an optical flow cytometer or through an impedance orifice in an impedance type flow cytometer. Most flow cytometers require mechanical subsystems to dilute the sample, to control the sample flow rate through the flow cell, and multiple sensors to evaluate the diluted sample. A special problem associated with hematology measurements is the wide dynamic range of particles that must be enumerated. The red blood cells (RBC's) are the most numerous at about 4.5×106 RBC's per microliter (μl), followed by the platelets at about 0.25×106 platelets per μl, and the white blood cells (WBC's) at about 0.05×106 per μl. Since all cells or particles must be enumerated during a full analysis, the range of cells/particles necessitates at least two dilution levels. The ability to perform multiple dilutions undesirably adds to the complexity of the machine. A person of skill in the art will recognize disadvantages associated with flow cytometers including plumbing leaks and inaccuracies due to fluid control miscalibration. In both of the aforementioned analyses, the operator (or the apparatus itself) must purge the biologic fluid sample from the apparatus and thoroughly clean the apparatus to avoid contaminating subsequent analyses. The substantial dilution required in both analyses also increases the likelihood of error, the complexity of the analysis, and the per analysis cost.
Other analytical methods minimize the above described problems by employing a disposable sample analytical chamber. In one chemical analytical method, the biologic fluid sample is placed in a flexible sealed pouch where it remains during the analysis. This approach avoids the need for plumbing, flow controls, and cleaning the container, but requires a large diluent volume and is restricted to standard measurements of light transmission. In the above method, the light path dimensions are controlled by the analytical instrument, which forms the flexible pouch into a cuvette of the desired thickness at the time of measurement. Other, similar “wet chemical”, systems employ a rigid analytical cuvette of specifically manufactured thickness. Other methods for performing a chemical analysis on a biologic fluid sample employ single or multiple test film substrates. The test film substrates also avoid the problems associated with dilution, flow controls, etc., but still require precise sample measurement and placement and are also limited to those analyses that employ light reflectance. The test film substrate methods are further limited by requiring that the associated disposable always have identically located analytical regions; if the desired information is not present in the predetermined analytical areas, then the test film substrate will not yield useful information. Hematological analytical methods which employ a disposable sample analytical chamber include the HemaCue™ and the QBC™. The HemaCue™ system is a method for measuring hemoglobin using a small cuvette. The HemaCue™ method is particularly useful for its intended purpose, but it is unable to measure particulate constituents of whole blood. The QBC™ system, a registered trademark of Becton Dickinson and Company of Franklin Lakes, N.J., USA involves placing a hematological fluid sample within a cylindrical tube and centrifuging the tube and sample for a given period of time. The centrifuge process separates fluid sample constituents into layers according to their density. A float disposed within the tube facilitates evaluation of constituents within each layer. Specific hematological tests may be performed in a disposable test system employing a scannable optical window in a device produced by Biometric Imaging. In this device, a substantially undiluted sample of whole blood is placed into a capillary of known and constant dimension where it is subjected to a laser scan which identifies some sub-types of WBC's. The Biometric Imaging method is also limited in that it is unable to measure any other constituents of whole blood.
Serologic or immunologic analyses measure soluble substances in blood, usually proteins such as specific immunoglobulins. These tests are often performed by admixing the sample with a sensitized particulate, such as latex, which will agglutinate in the presence of the protein of interest. Another method for performing a more quantitative immunological analysis is to use enzymatically linked color changes, such as ELISA. All of these methods are performed on apparatus specialized for their use.
Another common specialized test is urinalysis. The analysis of urine is generally divided into two separate phases: the determination of the bulk and/or chemical properties of the sample and the analysis of particulates within the sample. These analyses require distinctly different disciplines and are usually done separately. There are large and complicated machines that can perform both types of analyses, but they are extremely expensive and require moderate maintenance and operator skill.
None of the above described analytical methods is capable of performing hematological, chemical/immunochemical, and serologic analyses on sample constituents within the same instrument. As a result, it has been necessary to purchase apparatus devoted to performing chemical analyses and apparatus devoted to performing hematological analyses. It has also been necessary to train technicians to operate the various types of apparatus, and to provide laboratory space and maintenance for them. It has also been impossible to combine hematological and chemical analyses in the same apparatus for those analyses where it would be advantageous to combine the analyses. In an analysis to determine anemia, for example, it is preferable to perform both hematological analyses (e.g., hemoglobin, hematocrit, and reticulocyte count) and chemical or immunochemical analyses (e.g., iron or ferritin, and/or vitamin B12 or folate determinations) on the sample. None of the above described methods permit hematological and chemical analyses on a single sample of blood in a single disposable sample chamber. As a result, the laboratory technician must separate and transport the various samples to their separate instruments which are often in separate laboratories, thereby increasing the inefficiency of the process as well as the potential for loss or misidentification of the sample. Also, the results of the analyses may not be available at the same time which increases the difficulty of interpreting the analysis results.
What is needed is a single container for holding a biologic fluid sample that can be used for multiple analyses including but not limited to hematological, chemical, immunological, serological, and urine analyses, one in which multiple analyses can be performed on the same sample in one instrument which presents a common operator interface, one that is operable with substantially undiluted biologic fluid samples, one whose method of sample introduction into the container is similar for each set of analyses, and one that can be used effectively as a disposable.